Wireless communication systems, such as Wireless Local Area Networks (WLANs), Metropolitan Area Networks (commonly referred to as WiMAX), and other types of wireless networks, have become increasingly common in today's “always connected” society. These wireless communication systems are used in a variety of different contexts to provide a number of services including, for example, voice, video, packet data, broadcast, and messaging services.
In some wireless communication systems, one or more of the wireless devices in the network may communicate using multiple transmit antennas and multiple receive antennas. Devices communicating via multiple transmit and receive antennas can form a multiple-input multiple-output (MIMO) channel that may be used to increase data throughput and/or improve reliability of the communications between the devices. For example, a source device may simultaneously send multiple data streams over multiple transmit antennas to multiple receive antennas of a destination device, which may improve the data throughput from the source to the destination. In another example, the source device may send a single data stream using multiple transmit antennas to improve the reliability of reception by the destination device.
Some MIMO source devices use a technique known as beamforming to further improve the transmission capabilities of the source device. Beamforming is a spatial filtering mechanism used at a transmitter to improve the received signal power or signal-to-noise ratio at an intended receiver. In general, beamforming uses a combination of the transmission signals from multiple non-directional transmit antennas to simulate a larger directional antenna. The beamformed signals may then be “pointed” towards the destination device to improve the reception at the destination device.